New 'super-Earth' may hold water, experts say

Astronomers on Monday announced the discovery of 50 new planets circling stars beyond the sun, including one "super-Earth" that is the right distance from its star to possibly have water.

"If we are really, really lucky, this planet could be a habitat" like Earth, said Lisa Kaltenegger of the Max Planck Institute for Astronomy in Heidelberg, Germany.

The planet, dubbed HD85512b, circles an orange star somewhat smaller and cooler than our sun about 36 light-years away. The star, HD85512, is visible in the southern sky in the constellation Vela.

The newly found planet circles this star every 59 days, putting it at the edge of the "habitable zone" where water could exist if conditions were right.

In a teleconference, Kaltenegger said that the planet is at the warm edge of its star's habitable zone, as if "standing next to a bonfire." That means the planet would require a lot of cloud cover - which reflects starlight - to keep the surface cool enough to prevent any water from boiling, she said.

Astronomers have not determined whether the new super-Earth is rocky like the Earth or gassy like Jupiter, let alone whether it has an atmosphere. The new super-Earth is 3.5 times the mass of Earth.

Astronomers inferred the existence of the planet by watching its star wobble ever so slightly. The speed of the wobble indicated the existence of a planet tugging at the star.

This "radial velocity" technique has been productive, offering astronomers working at La Silla Paranal Observatory in Chile evidence of the 50 new "exoplanets" announced Monday. The planet-hunting instrument, called HARPS, is operated by the European Southern Observatory.

Sixteen of the new planets announced Monday, including the new super-Earth, are of the right mass to be made of rock instead of gas.

"We are building up a target list of super-Earths in the habitable zone," Kaltenegger said.

To determine whether the planet has an atmosphere, astronomers need to capture an image of the planet and analyze the light for signs of water, carbon dioxide and other gases.